November 20, 2013 3:36 pm
Hermit crabs have an odd housing situation. Rather than produce their own shells like other crustaceans, they must find an empty shell made by a completely different species, marine snails, in order to protect their delicate abdomen. Hermit crabs that find the perfect shells, research has shown, have a greater chance of surviving than those who get stuck with a non-ideal house, so finding a shell with a good fit is a pretty big deal for these little guys.
As they grow, hermit crabs must abandon their old shell and find a new one they can comfortably squeeze into. If there aren’t enough shells to go around, hermit crab populations will actually shrink. Despite the gravity of shell availability for the crabs’ survival, research don’t really understand much about how hermit crabs select their shells. For example, they don’t know whether hermit crabs change their shell preferences over time—much as a person may change her fashion style as she grows up—or whether they stick to one shell type throughout their lifetime. They also puzzle over whether different species of hermit crabs compete for the same shells.
In a new study, researchers trapped dozens of hermit crabs of four different sizes and ages, and from two different species. They gently removed the crabs from their shells, and presently them individually with a choice of six empty, size-matched shells from six different species of snails common to the study site, in Vancouver. They also carried out field surveys to see how hermit crabs were handling shell decisions in nature.
The animals’ preferences, they found, do indeed change throughout their life. As the crabs got older, their tolerance for shell diversity decreased, and they honed in on a single shell type they liked best. “In addition, similar-sized hermit crabs of the 2 species mostly ignored the shell types used by the other species, a resource partitioning that would facilitate coexistence,” the researchers report. In other words, hermit crabs avoid making waves with cousins of different species by establishing their own unique shell preferences. Whether the crabs would break that shell-sharing truce if their ideal abode suddenly went into short supply, however, is a matter left to future research.
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November 20, 2013 10:16 am
The concept of paying it forward, or reciprocating a kind act from one person by doing something kind for another, has been in the limelight lately, with Starbucks’ pay it forward campaign and other acts of kindness attracting media attention, but the idea that good deeds generate more good deeds dates back to the days of the ancient Greeks. New research, however, bursts the benevolence bubble. Although people do sometimes pay it forward, researcher Michael Norton writes in Scientific American, on the whole, we are much more likely to pass on negative actions than positive ones.
Norton and his colleagues performed an experiment in which they gave one person (an actor) six dollars and told the person to keep all the money, split it or pass all of it on to another person (the study subject, who didn’t know the other person was an actor). Then, the subject was asked to make the same choice—keep the cash, split it or give it all away to another stranger. Here’s what the researchers found:
First, some good news: people who had been treated fairly were very likely to pay forward fairness: if someone splits $6 evenly with me, I’ll split $6 evenly with the next person. Now, some worse news: people who had received generosity – who’d gotten the full $6 from the previous person –were willing to pay forward only $3. In other words, receiving generosity ($6) did not make people pay forward any more cash than receiving fairness ($3). In both cases, people were only willing to pay forward half. Now the bad news: people who had received greed? They were very likely to pay that greed forward, giving the next person just a little over $1, on average.
In other words, the subjects who were shortchanged were taking their frustrations about their bad experience out on a perfect stranger. They were more likely to pay greed forward than generosity, Norton explains, which can be summed up as, “If I can’t pay you back for being a jerk, my only option for feeling better is to be a jerk to someone else.”
At the same time, people have little incentive to be nice to one another unless they are part of a specific group that creates some sense of shared identity, Norton says. Based on these findings, you’ll probably want to have cash on hand next time you visit Starbucks. That stranger ahead of you in line most likely won’t be picking up your tab.
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November 20, 2013 9:40 am
On average, men are larger than women. But their tendency towards bigger noses—which are about 10 percent larger than women’s—turns out to have a hidden evolutionary purpose. Bigger noses, new research finds, are needed in order satisfy the higher energetic needs of men’s bodies, especially during puberty.
Nose sizes begin to diverge between the sexes around age 11, or just as kids begin to enter into puberty. During that time, the researchers explain, women tend to accumulate fat mass, while men’s bodies build muscle. This trend remains the same throughout life, as adult men, in general, have more lean muscle than women.
The researchers investigated these differences in a long-term study of 40 girls and boys. Between the ages of 3 and 20, the team took detailed measurements and X-rays of their subjects’ bodies. Nose size in the boys increased at a disproportionate rate to body size compared to the girls, NBC New reports. ”Even if the body size is the same, males have larger noses, because more of the body is made up of that expensive tissue,” the researchers explain in a statement.
The team concluded that those differences likely evolved because a bigger schnoz can suck up more air than a dainty one, and it takes a greater supply of oxygen to power the excess of energetically demanding muscle that men have, compared to women. This also speaks to differences between modern humans and our ancient ancestors, the researchers say. Ancient humans had more muscle mass than we soft creatures of today, and thus needed extra-large noses.
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November 19, 2013 3:23 pm
People with synesthesia—adults and kids—have their senses crossed: for some, sounds have colors, for others words have smells. It’s sort of like living in an elementary school classroom, where everything’s bright and colorful, and alive—only few other people are experiencing the same show. But according to new research, highlighted by Elizabeth Preston on her blog, Inkfish, its possible for people to outgrow their synesthesia.
The odd connections derive from a brain that’s linked in unexpected ways, where the neural centers for various senses are in heightened contact. Testing a series of children as the grew up, says Preston, two researchers, Julia Simner and Angela Bain, tracked how some kids lost their synesthesia over time.
Young synesthetes losing their colors over time would fit with a popular theory about synesthesia, which says that it comes from an overly connected brain. “All very young children have hyper-connected brains,” Simner says; the neurons branch out indiscriminately between different areas. As we grow, the unneeded connections are pruned away, a process that continues throughout childhood. “It may be that synesthetes escape the pruning, so to speak,” Simner says. All kids might start out with some degree of synesthesia, which fades away with normal development.
Some peoples’ synesthesia survives the childhood pruning, and, in those cases, actually seems to get reinforced. But if it’s true that many more kids than we thought are synesthetic that could go a long way toward explaining some kids’, er, creative artistic endeavors.
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November 19, 2013 3:21 pm
Male competitiveness for mates is well studied by researchers. It fits into a long-running narrative about how society works: active men compete for passive women. But lately, researchers began to examine the possibility that women are subjected to the pressures of competition just as stiffly as their male counterparts. And new research shows that aggressive female behaviors likely evolved years ago as ways for women to assert dominance and maintain control of the best mates.
The old doubts about female competitiveness derived partly from an evolutionary analysis of the reproductive odds in ancient polygynous societies in which some men were left single because dominant males had multiple wives. So men had to compete to have a chance of reproducing, whereas virtually all women were assured of it.
But even in those societies, women were not passive trophies for victorious males. They had their own incentives to compete with one another for more desirable partners and more resources for their children. And now that most people live in monogamous societies, most women face the same odds as men. In fact, they face tougher odds in some places, like the many college campuses with more women than men.
In the study, researchers recruited pairs of female students, who did not know the real purpose of the experiment. While waiting in a lab, an actress hired by the researchers entered the room, ostensibly looking for directions to another lab.
The actress had some scientifically verifiable characteristics of an attractive person, like an hour-glass figure. But sometimes she wore baggy clothing when she barged into the lab, and other times she entered wearing a tight, low-cut shirt and a miniskirt. Unbeknownst to the female participants, their remarks and reactions were secretly being recorded. “In jeans, she attracted little notice and no negative comments from the students,” the Times describes, “but when she wore the other outfit, virtually all the students reacted with hostility.”
The results of the experiment jibe with evidence that this “mean girl” form of indirect aggression is used more by adolescents and young women than by older women, who have less incentive to handicap rivals once they marry. Other studies have shown that the more attractive an adolescent girl or woman is, the more likely she is to become a target for indirect aggression from her female peers.
The researchers’ take-away here is that women, not men, are most likely the predominant reason that promiscuous women are oftentimes ostracized from society. This makes sense from an evolutionary perspective. Women control a valuable resource–sex–which gives them power over men. Loose women threaten to disrupt that balance of power by making the resource too readily available, the Times explains.
But, as many writers who regularly cover gender and sexuality have noted, it’s not clear that it’s necessary to make that leap. Refinery 29 writes, ”Kim Wallen, a psychologist at Emory University, notes that Vaillancourt’s piece was only based off of other studies, “none of which contain data showing that indirect aggression is successful in devaluing a competitor.” In other words, if women are acting aggressive towards other women in order to keep them away from men, it’s not necessarily working.
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